1. Field of the Invention
This invention relates to electronic tone synthesis and in particular is concerned with selecting a subset of a set of accompaniment tones which will complement preselected solo tones generated by an electronic musical instrument.
2. Description of the Prior Art
An electronic keyboard musical instrument, such as an electronic organ, is usually implemented with a number of tone switches for selecting the tones produced in response to actuated keyswitches. The tone switches are generally organized in groups which correspond to the tiers of keyboards each of which is composed of a linear array of keyswitches. Before starting to play such an instrument, the musician must confront the problem of selecting the combination of tone switches to be actuated for each of the keyboards. Since even a medium size instrument may contain about 10 tone switches per keyboard, the theoretical number of combinations of tone switches for a single keyboard is 2.sup.10 -1=1023. Obviously, theoretically the musician is faced with a very large number of choices. Certain considerations, largely based upon a degree of musical maturity, are used in practice to greatly reduce the number of tone stop combinations which are eligible candidates to be selected. However, even the application of emperical tone selection rules still leaves a large number of residual switch selection choices.
Organs designed primarily for the performance of popular music are called by the generic name of "entertainment" organs. These instruments are usually designed to use solo type voices on the upper keyboard (also called the solo keyboard) and accompaniment type voices are available on the lower (also called the accompaniment keyboard) and pedal keyboards. A common tonal selection employed by the musician is to imitate a small combo group by selecting a solo stop for the upper keyboard along with a blending, or complementary, tone color for the lower keyboard and a similar blending tone for the pedal keyboard.
The choice of an accompaniment tone is, of course, ideally dependent upon the choice that has been made for the solo tones. Based upon years of experience with a wide variety of musical effects, some emperical rules have been formulated for the selection of accompaniment tones which complement specific solo tones. These rules are predicated upon a classification of organ tones. Before the rather recent advent of the tone synthesizer having time varying frequency domain sliding formant filters, organ tones were traditionally categorized as belonging to one of four tone classes. These classes comprised flutes, diapasons, strings, and reeds. These tone families are not sharply defined and in many border-line cases the classification of a tone type is somewhat subjective. A close examination of elements of these tone classes indicates that the classes differ primarily in the number of prominent harmonics as well as with the rate at which the harmonic levels decrease with an increase in the harmonic number.
Most of the emperical tone selection rules usually consist of instructions for selecting a tone from a given tone family for the accompaniment tone to complement a solo tone which has been selected from one of the tone classes. While these selection rules are not intended as firm regimens, they at least provide a certain degree of guidance for a novice musician who is faced with the tone section problem.
A means for generating an accompaniment tone color which complements a preselected solo tone color is described in the copending patent application Ser. No. 06/344,093 filed Jan. 20, 1982 entitled "Adaptive Accompaniment Tone Color For An Electronic Musical Instrument." The referenced application and the present invention have a common assignee. In the copending application apparatus is described for generating an accompaniment tone color by analyzing the selected tone musical waveshape and then performing a synthesis computation. The accompaniment tone color is not selected from a preselected library of waveshape data.